This invention relates to a linear motor, and more particularly to a linear motor in which a moving member is interposed or sandwiched through a gap between magnetic pole teeth of an armature opposite to each other.
The conventional linear motor comprises a stator having a plurality of magnetic pole members and a moving member supported so as to be movable relatively to the stator through a gap. In general, the conventional linear motors are of a type cutting and opening a rotary machine and developing the opened rotary machine on a straight line.
Of such conventional linear motors, disclosed in the Japanese Patent Application Laid-Open No. 10-174481 (1998) is a linear motor in which a moving member is interposed through gaps between magnetic pole teeth of an armature opposite to each other to be relatively moved in order to reduce burdens on the moving member supporting mechanism by canceling out forces acting between the stator and the moving member.
However, the conventional linear motor is complicated in construction since a plurality of windings are wound on one stator unit. Further, adjacent stator magnetic pole members are wound with windings different from each other. Therefore, there is much waste in the space that the stator occupies.
An object of the present invention is to provide a linear motor which comprises a plurality of magnetic pole teeth while compact in construction because of the low number of windings and is capable of canceling out magnetic attracting forces acting between an armature and a moving member, in order to overcome the above defects of the conventional linear motor.
Another object of the present invention is to provide a linear motor in which an amount of change in inductance to an amount of relative displacement between the armature and the moving member is so reduced that thrust ripples are reduced.
According to an aspect of the present invention, a linear motor is provided which comprises an armature; a moving member movable relatively to the armature; first and second magnetic pole tooth trains each comprising magnetic pole teeth magnetically coupled to one of two magnetic poles of the moving element, the first and second magnetic pole tooth trains being separated from each other in a direction substantially perpendicular to a moving direction of the moving member; and third and fourth magnetic pole tooth trains each comprising magnetic pole teeth magnetically coupled to the other of the two magnetic poles of the moving element, the third and fourth magnetic pole tooth trains being separated from each other in a direction substantially perpendicular to a moving direction of the moving member; the magnetic pole teeth of the first magnetic pole tooth train and the magnetic pole teeth of the third magnetic pole tooth train being alternately arranged in the moving direction of the moving member, the magnetic pole teeth of the second magnetic pole tooth train and the magnetic pole teeth of the fourth magnetic pole tooth train being alternately arranged in the moving direction of the moving member, and the moving member being arranged between the first and second magnetic pole tooth trains and the third and fourth magnetic pole tooth trains.
According to another aspect of the present invention, a linear motor is provided which further comprises means for reducing an amount of change in inductance to an amount of relative displacement between the armature and the moving member so as to reduce detent forces.